Main Virgo data
Principle: Michelson laser interferometer with two Fabry-Perot cavities in the arms and power recycling.
Arms length: 3 kilometers
Vacuum tube: 120 cm diameter, fully welded (no seal)
Vacuum performance:
  Pressure after baking at 150o C: < 10-9 mbar
  hydrocarbons partial pressure 10-13 mbar
Laser and injection system:
  Nd:YAG diode-pumped laser at 1064 nm  
  Laser power: 20 W
  Mode cleaner: 144 m long, 3 mirrors ring cavity
  Finesse of mode cleaner cavity 1000
  Frequency stability < 10-4 Hz1/2 at 1 kHz
  Relative Intensity Noise (RIN) < 10-7 at 1 kHz
  Power Stored in Fabry-Perot cavity: 15 to 50 kW (depending of finesse)
  Power Stored in recycling cavity: 1 kW
Optics
  Main mirror substrates special “Virgo” grade fused silica
  absorption < 1 ppm/cm
  diameter 350mm
  Reflective coatings absorption < 1ppm
  Anti reflection coatings reflection < 0.1 %
  Surface quality l/200 rms
  Surface microroughness < 1 Angstrom
Suspensions

Inverted pendulum pre-isolator plus 6 passive stages.  

Active control on first and last stage and on mirror.  
  Seismic attenuation 10-11 at 10 Hz
  rms mirror motion before locking: <1 mm, < 0.1 mradian
  Thermal stabilization +/- 0.1 degree C
Frequency range 10 Hz to 10 kHz
Sensitivity h ~ 3 10-21 Hz-1/2 at 10 Hz
h ~ 3 10-23 Hz-1/2 at 1 kHz
Provision for future implementation of signal recycling technique
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